headliner falling down in back

[monroegt]

Hey guys I just bought a 2000 gt and my headliner in the back near the rear window is sagging down. Word of mouth is that all it is is a simple glue that the factory uses to keep it in place. But the guy I bought the car from put his own tint on and did a realy bad job so it would suprise me if he rigged up the headliner. Any help on how to fix this would be greatly appreciated.